FIG. 35 shows a conventional LED lamp (see Patent Document 1, for example). The LED lamp X illustrated in the figure includes a substrate 91 in the form of an elongated rectangle, a plurality of LEDs 92 mounted on the substrate 91, a tube 93 accommodating the substrate 91, and terminals 94. The substrate 91 is formed with a wiring pattern (not shown) connected to the LEDs 92 and the terminals 94. The LED lamp X is structured such that the LEDs 92 can be turned on when the terminals 94 are fitted into inlet ports of sockets of a general-use fluorescent lighting fixture.
The general-use fluorescent lighting fixture herein refers to lighting fixtures widely used for interior lighting as the main application, and more specifically, lighting fixtures which use, for example in Japan, a commercial 100 V or 200 V power supply and to which a JIS C7617 straight-tube fluorescent lamp or a JIS C7618 circular fluorescent lamp can be attached.
In the LED lamp X, on the substrate 91 is mounted a circuit 95 for converting alternating current supplied from a commercial power supply into direct current and supplying the current to the LEDs as a constant current. The circuit includes a plurality of power supply parts. Thus, it is preferable that the circuit 95 having this structure is arranged adjacent to the terminals 94, which are the power supply regions, i.e., adjacent to ends of the LED lamp X.
In the above-described conventional LED lamp X, however, a space exists between the tube 93, which serves as a cover, and the LEDs 92. Thus, because of the difference in index of refraction between these parts, part of the light is reflected at the inner surface of the tube 93. Thus, to achieve a sufficient amount of light emission from the lamp, a large number of LEDs 92 needs to be used or a large current needs to be supplied to the LEDs.
The circuit 95 is mounted on the reverse surface (the surface opposite to the surface on which the LEDs 92 are mounted) of the substrate 91. Considering the influences of the heat generated at the LEDs 92, the power supply parts constituting the circuit 95 should not be placed at positions that overlap the LEDs 92 as shown in FIG. 35. Instead, the power supply parts are preferably deviated in the longitudinal direction of the substrate 91 to be placed at the ends of the substrate spaced in the longitudinal direction so as not to overlap the LEDs 92. However, when the power supply parts are placed so as not to overlap the LEDs 92, LEDs 92 cannot be placed adjacent to the ends of the substrate 91. This increases the non-light-emitting area of the LED lamp X, which is not desirable.
To make the LED lamp X having the above-described structure, the substrate 91 is first inserted into the tube 93. Then, the terminals 94 need to be attached to the ends of the tube 93, while keeping the positional relationship between the tube 93 and the substrate 91 unchanged. In this way, the process for manufacturing the conventional LED lamp X is troublesome.
Further, in the conventional LED lamp X, directivity of the light from the LEDs 92 is high. Thus, mounting of such LEDs 92 on a single substrate 91 cannot achieve uniform illumination over an entire area from a ceiling to a bottom, for example.
Further, when the conventional LED lamp X is used as a substitute for a straight-tube fluorescent lamp, e.g. for a FL40W type having a long tube length (tube length 1198 mm), the LEDs 92 need to provide a light emission area of about 1100 mm that substantially corresponds to the tube length. To achieve uniform illumination by the LED lamp. X, the LEDs 92 need to be arranged at equal intervals. When the interval between the LEDs 92 is large, relatively dark portions are provided between adjacent LEDs, resulting in non-uniform brightness. To avoid such non-uniform brightness, it is necessary to increase the number of the LEDs 92 and reduce the interval between the LEDs 92.
However, when the number of the LEDs 92 is increased, the power consumption of the LED lamp X increases. For the power consumption of the LEDs 92 to be suppressed to a level equal to or lower than that of a fluorescent lamp, the interval between the LEDs 92 cannot be reduced to a level that eliminates the non-uniformity of brightness between adjacent LEDs 92.
Moreover, in the LED lamp X, heat is generated during the lighting of the LEDs 92. Thus, the temperature of the substrate 91 and the LEDs 92 undesirably increases to result in the breakage of the wiring pattern on the obverse surface of the substrate 91 and the LEDs 92.
The circuit 95 is mounted on the reverse surface (the surface opposite to the surface on which the LEDs 92 are mounted) of the substrate 91. Considering the influences of the heat generated at the LEDs 92, the power supply parts constituting the circuit 95 should not be placed at positions that overlap the LEDs 92 as shown in the figure. Instead, the power supply parts are preferably deviated in the longitudinal direction of the substrate 91 to be placed at the ends of the substrate spaced in the longitudinal direction so as not to overlap the LEDs 92. That is, it is preferable that the power supply parts are arranged separately in a region (power supply region) different from the region (light source region) where the LEDs 92 are arranged.
However, when the power supply parts are arranged in the power supply region (ends of the substrate 91) separate from the light source region where the LEDs 92 are placed, LEDs 92 cannot be arranged adjacent to the ends of the substrate 91. As a result, the regions adjacent to the ends of the substrate 91 become a non-light-emitting area. This leads to a degraded illumination quality of the lamp X, which is not desirable.
FIG. 36 is a block diagram showing an LED lighting apparatus provided by attaching an LED lamp to a conventional general-use fluorescent lighting fixture. The general-use fluorescent lighting fixture herein refers to lighting fixtures widely used for interior lighting as the main application, and more specifically, lighting fixtures which use, for example in Japan, a commercial 100 V or 200 V power supply and to which a JIS C7617 straight-tube fluorescent lamp or a JIS C7618 circular fluorescent lamp can be attached. The LED lighting apparatus B′ includes a general-use fluorescent lighting fixture C and an LED lamp A′.
The general-use fluorescent lighting fixture C is originally designed to input alternating current from a commercial 100 V power supply D to a fluorescent lamp mounted to the lighting fixture. The general-use fluorescent lighting fixture C includes a ballast C1. The ballast C1 is designed to generate a high voltage in a fluorescent lamp to start a discharge and stabilize the current inputted into the fluorescent lamp after the start of the discharge. General-use fluorescent lighting fixtures C are classified into a starter type, a rapid start type, an inverter type and so on, depending on the mode of the lighting of fluorescent lamps. In the state in which the LED lamp A′ is attached to the lighting fixture, the voltage, current and frequency outputted from the ballast C1 vary depending on the lighting mode even when the rated voltage is the same. Moreover, even when the lighting mode is the same, the characteristics of the ballast C1 slightly vary depending on the kinds of the general-use fluorescent lighting fixture C.
The LED lamp A′ emits light when alternating current from a commercial 100 V power supply is inputted into the lamp via the ballast C1 of the general-use fluorescent lighting fixture C. The LED lamp A′ includes a rectifying circuit 100, a protective part 200 and an LED lighting circuit 300. The rectifying circuit 100 converts an alternating current inputted from the ballast C1 into a direct current and outputs the direct current to the LED lighting circuit 300. The LED lighting circuit 300 turn on the white LEDs 310a incorporated in it by using the direct current inputted from the rectifying circuit 100. The specification and number of the white LEDs 310a connected in series to form an LED row 310 and the resistance of the resistor 320 in the LED lighting circuit 300 are determined based on the rated voltage of the general-use fluorescent lighting fixture C to which the lamp is attached.
Since the voltage, current and frequency to be inputted vary depending on the ballast C1, the resistor 320 is provided in the LED lighting circuit 300 to prevent excessive current from flowing to the white LEDs 310a . Further, it is also proposed to connect a constant current circuit such as a constant current diode to the input side of the white LEDs 310a to keep the current flowing to the white LEDs 310a constant.
However, the resistor 320 consumes electric power by conversion into heat and hence deteriorates the use efficiency of electric power. Further, to connect a constant current circuit, a region for arranging such a circuit needs to be secured in the LED lighting circuit 300. Since white LEDs 310a cannot be placed in this region, the non-light-emitting area, which is dark, increases. Moreover, the use of a constant current circuit increases the manufacturing cost.
Patent Document 1: JP-U-6-54103